Bottom Line:
Plant species diversity is often claimed to positively affect habitat preferences of insect predators, but the effects of within-species genotype diversity have not been extensively studied.In laboratory experiments on adult ladybird orientation to odour from barley, ladybirds were attracted/arrested by the mixed odour of the same barley genotype mixture that was preferred in the field.Exposure of one barley genotype to volatiles from the other also caused the odour of the exposed plants to become more attractive to ladybirds.

ABSTRACTThe effects of within-species plant genotype mixing on the habitat preference of a polyphagous ladybird were studied. Plant species diversity is often claimed to positively affect habitat preferences of insect predators, but the effects of within-species genotype diversity have not been extensively studied. In a field experiment with different barley (Hordeum vulgare) genotypes in mixed and pure stands, adult seven-spot ladybird Coccinella septempunctata, a polyphagous predator, preferred a specific combination of genotypes over the single genotypes alone before aphids had arrived in the crop, and again when aphids were emigrating. In laboratory experiments on adult ladybird orientation to odour from barley, ladybirds were attracted/arrested by the mixed odour of the same barley genotype mixture that was preferred in the field. Exposure of one barley genotype to volatiles from the other also caused the odour of the exposed plants to become more attractive to ladybirds. The results support the hypothesis that plant volatiles may attract or arrest foraging adult ladybirds, contributing to the selection of favourable habitats, and they show that within-species plant genotype mixing can shape interactions within multitrophic communities.

Fig1: Occurrence of the ladybird C. septempunctata in plots with mixtures of barley genotypes and genotypes grown in pure stands at time points during the crop season. Figures show mean numbers of ladybirds per plot in binary mixtures of genotypes compared with both single genotypes. *P < 0.05, **P < 0.01, LSD pair-wise comparisons

Mentions:
During the initial phase, peak C. septempunctata abundance was significantly higher in the Alva–Hulda mixture compared to pure plots (Fig. 1), whereas this effect was not observed for any of the other five two-genotype mixtures tested (data not shown). The initial peak corresponds to ladybird immigration to the barley crop before aphids have arrived (Fig. 2) (as also illustrated by the suction trap data in Fig. 3). On 6 June 2000, during the initial immigration phase, the Hulda–Alva genotype mixture had a significantly higher number of ladybirds than pure plots of Hulda (P = 0.003) or Alva (P = 0.012).Fig. 1

Fig1: Occurrence of the ladybird C. septempunctata in plots with mixtures of barley genotypes and genotypes grown in pure stands at time points during the crop season. Figures show mean numbers of ladybirds per plot in binary mixtures of genotypes compared with both single genotypes. *P < 0.05, **P < 0.01, LSD pair-wise comparisons

Mentions:
During the initial phase, peak C. septempunctata abundance was significantly higher in the Alva–Hulda mixture compared to pure plots (Fig. 1), whereas this effect was not observed for any of the other five two-genotype mixtures tested (data not shown). The initial peak corresponds to ladybird immigration to the barley crop before aphids have arrived (Fig. 2) (as also illustrated by the suction trap data in Fig. 3). On 6 June 2000, during the initial immigration phase, the Hulda–Alva genotype mixture had a significantly higher number of ladybirds than pure plots of Hulda (P = 0.003) or Alva (P = 0.012).Fig. 1

Bottom Line:
Plant species diversity is often claimed to positively affect habitat preferences of insect predators, but the effects of within-species genotype diversity have not been extensively studied.In laboratory experiments on adult ladybird orientation to odour from barley, ladybirds were attracted/arrested by the mixed odour of the same barley genotype mixture that was preferred in the field.Exposure of one barley genotype to volatiles from the other also caused the odour of the exposed plants to become more attractive to ladybirds.

ABSTRACTThe effects of within-species plant genotype mixing on the habitat preference of a polyphagous ladybird were studied. Plant species diversity is often claimed to positively affect habitat preferences of insect predators, but the effects of within-species genotype diversity have not been extensively studied. In a field experiment with different barley (Hordeum vulgare) genotypes in mixed and pure stands, adult seven-spot ladybird Coccinella septempunctata, a polyphagous predator, preferred a specific combination of genotypes over the single genotypes alone before aphids had arrived in the crop, and again when aphids were emigrating. In laboratory experiments on adult ladybird orientation to odour from barley, ladybirds were attracted/arrested by the mixed odour of the same barley genotype mixture that was preferred in the field. Exposure of one barley genotype to volatiles from the other also caused the odour of the exposed plants to become more attractive to ladybirds. The results support the hypothesis that plant volatiles may attract or arrest foraging adult ladybirds, contributing to the selection of favourable habitats, and they show that within-species plant genotype mixing can shape interactions within multitrophic communities.